Oh, regrtest main process was killed by faulthandler watchdog: it was blocked in _get_result() for longer than 1 minute.

Extract of _get_result():

        use_faulthandler = (self.ns.timeout is not None)
        timeout = PROGRESS_UPDATE
        while True:
            if use_faulthandler:
                faulthandler.dump_traceback_later(timeout * 2.0, exit=True)

            # wait for a thread
            try:
                return self.output.get(timeout=timeout)
            except queue.Empty:
                pass

            # display progress
            running = get_running(self.workers)
            if running and not self.ns.pgo:
                self.log('running: %s' % ', '.join(running))

self.ns.timeout is supposed to be 1500.

I don't understand why regrtest got a timeout of 60 seconds?

https://buildbot.python.org/all/#/builders/168/builds/1583

LD_LIBRARY_PATH=/usr/home/buildbot/python/3.x.koobs-freebsd-current/build ./python  ./Tools/scripts/run_tests.py -j 1 -u all -W --slowest --fail-env-changed --timeout=1500 -j2 -j4 
== CPython 3.9.0a0 (heads/master:ed8efd8e2c, Oct 7 2019, 21:38:27) [Clang 8.0.1 (tags/RELEASE_801/final 366581)]
== FreeBSD-13.0-CURRENT-amd64-64bit-ELF little-endian
== cwd: /usr/home/buildbot/python/3.x.koobs-freebsd-current/build/build/test_python_67537
== CPU count: 4
== encodings: locale=UTF-8, FS=utf-8
Using random seed 1307598
0:00:00 load avg: 3.41 Run tests in parallel using 4 child processes
(...)
0:00:11 load avg: 3.55 [ 12/419] test_extcall passed
0:00:13 load avg: 3.55 [ 13/419] test_pydoc passed
0:00:14 load avg: 3.55 [ 14/419] test_devpoll skipped
test_devpoll skipped -- test works only on Solaris OS family
0:00:15 load avg: 3.55 [ 15/419] test_class passed
0:00:17 load avg: 3.50 [ 16/419] test_ntpath passed
Timeout (0:01:00)!
Thread 0x0000000802d30c00 (most recent call first):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/selectors.py", line 415 in select
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/subprocess.py", line 1964 in _communicate
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/subprocess.py", line 1113 in communicate
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 199 in _run_process
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 228 in _runtest
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 265 in run
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 944 in _bootstrap_inner
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 902 in _bootstrap

Thread 0x0000000802d2fd00 (most recent call first):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/selectors.py", line 415 in select
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/subprocess.py", line 1964 in _communicate
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/subprocess.py", line 1113 in communicate
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 199 in _run_process
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 228 in _runtest
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 265 in run
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 944 in _bootstrap_inner
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 902 in _bootstrap

Thread 0x0000000802d2f800 (most recent call first):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/selectors.py", line 415 in select
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/subprocess.py", line 1964 in _communicate
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/subprocess.py", line 1113 in communicate
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 199 in _run_process
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 228 in _runtest
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 265 in run
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 944 in _bootstrap_inner
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 902 in _bootstrap

Thread 0x0000000802d30200 (most recent call first):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/selectors.py", line 415 in select
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/subprocess.py", line 1964 in _communicate
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/subprocess.py", line 1113 in communicate
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 199 in _run_process
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 228 in _runtest
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 265 in run
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 944 in _bootstrap_inner
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 902 in _bootstrap

Thread 0x0000000800acc000 (most recent call first):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/threading.py", line 307 in wait
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/queue.py", line 179 in get
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 362 in _get_result
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 413 in run_tests
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/runtest_mp.py", line 434 in run_tests_multiprocess
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/main.py", line 513 in run_tests
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/main.py", line 687 in _main
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/main.py", line 634 in main
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/libregrtest/main.py", line 712 in main
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/__main__.py", line 2 in <module>
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/runpy.py", line 85 in _run_code
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/runpy.py", line 192 in _run_module_as_main
*** Error code 1